The world already knows how Angela Merkel feels about Silvio Berlusconi. The former Italian prime minister allegedly sought pleasure with underage prostitutes, he wasn’t particularly fastidious about the rule of law and he sought to grin away his country’s problems. Italian newspapers also reported a few years ago that he made some rather untoward remarks about the German chancellor’s posterior in a telephone conversation. Berlusconi was precisely the kind of politician Merkel abhors.

Nevertheless, she usually got what she wanted from him. At an EU summit in December 2008, she deployed a mix of charm and toughness to secure his agreement on her climate policies. It was a fabled event, and diplomats still tell stories today about how she wrapped the vain Italian leader around her little finger.

Merkel’s people are hoping for some similar magic at an upcoming encounter that will be even more sensitive. On Tuesday, she will meet with U.S. President Donald Trump in Washington, D.C. It will be the first in-person meeting between the two since the U.S. election in November. And it could be the most difficult meeting Merkel has ever faced as chancellor.

During and after the election, people made all sorts of wild and absurd equivalences between Trump and people like Adolf Hitler and other monsters of history. Most people missed the similarity in style and approach between Trump and Berlusconi, which was more apparent while simultaneously being much less hyperbolic. Both of them rode populists waves to high office after successes in media and other industries. Berlusconi had the same kind of bravado and public arrogance, and backed it up with a similar track record in the private sector before taking on politics at the highest levels. Berlusconi ended up shooting himself in the foot with his undisciplined appetites, but he succeeded for almost two decades at the highest levels of Italian politics.

Direct confrontation with Berlusconi worked less well than getting him to come around through patient negotiation and friendly approaches. That seems to work well with Donald Trump too, in part because of his transactional rather than ideological nature, and in part because Trump wants to make deals rather than break them — just better deals than his predecessors. Der Spiegel reports that her aides think it’s possible to stand on principle in some areas while leaving Trump room to maneuver in others:

The chancellor will seek to establish a good relationship with the president. Trump relies less on the traditional mechanism of politics than his predecessors and he often makes decisions impulsively, without regard to well-established procedures.

“Trump’s actions are driven more by his instincts and business experience than by political rationality,” says Norbert Röttgen, the foreign policy spokesman for Merkel’s center-right Christian Democratic Union (CDU). He traveled to Washington a few weeks ago for talks. “That doesn’t make dealing with him any easier.”

Politico’s Nahal Toosi reports that Trump will engage Merkel with an open mind, and with an eye on the international reaction to their relationship. He’s not likely to get what he wants on trade, however, as Merkel is too committed to the EU for bilateral changes:

Senior Trump administration officials said Friday that the president is heading into Tuesday’s meeting with Merkel with an open mind, and that he is “very interested in hearing her insights” on how to deal with Russia. The officials also made it clear that Trump still expects more NATO members to step up their defense spending — a position that’s in line with that of Trump’s Democratic predecessor, Barack Obama, who was more cautious in his rhetoric.

Trade is also likely to be a topic of the talks, including the future of proposed EU-U.S. deal known as the Transatlantic Trade and Investment Partnership. A top Trump administration trade official recently bemoaned the $65 billion U.S. trade deficit with Germany, and suggested the two countries discuss it bilaterally. But German officials are reported to have dismissed that idea, noting that Germany does trade agreements through the EU.

And Merkel in general is likely to frown on any U.S. advances that appear to weaken the EU, an institution that has helped Germany move past its own ugly history of dalliance with nationalism.

“Germany is going to always be within the cloak of Europe,” said Sudha David-Wilp, a Berlin-based senior trans-Atlantic fellow with the German Marshall Fund of the United States. “Sure the country has its own interests, but it also sees its two biggest interests as having good relations with the United States but also enabling and empowering Europe.”

Climate advocates and European officials see Merkel’s visit as the first opportunity to lay the groundwork to persuade Trump to keep the U.S. in the landmark Paris climate agreement, and to back a joint G20 leaders’ declaration emphasizing their commitment to limiting greenhouse gas emissions.

rump vowed during the campaign to “cancel” the Paris agreement, which the U.S. and nearly 200 other nations backed in 2015, and top advisers like Stephen Bannon are seen as opposing the deal. But other advisers including the president’s daughter Ivanka Trump are quietly considering a plan to stay in the agreement, while weakening former President Barack Obama’s pledge to slash U.S. greenhouse gas emissions.

Although global warming is undoubtedly a priority for Germany’s “climate chancellor,” it’s not certain that the issue will make it onto Tuesday’s agenda, which could also include issues like NATO, trade and EU relations, sources said.

“Leaders at this point tend to be a little cautious and pick their fights,” an EU source following the international climate talks said. “Will Merkel do it? I don’t know, but if she doesn’t it wouldn’t surprise me.”

That will likely be too much for Merkel to bite off at the moment. Trump has made clear that he wants to revitalize American energy production and push the EPA away from enforcement of carbon-emission limits. That is a major piece of Trump’s “America First” approach to economic growth, and a way to impact national-security concerns, too. The topic will almost certainly come up in multilateral conferences over the next few months — G7, G20, and NATO — and Merkel may want to have more voices at the table when raising global-warming concerns.

Will Trump get wooed by Merkel? Because Trump tends more toward the transactional than the ideological, he has shown considerable flexibility when engaging prominent voices on controversial issues; his meetings with Al Gore on global warming and John Kasich on ObamaCare come to mind. Nothing resulted from the Gore meeting, though, and Trump has shown over the last couple of months that even his transactionalism has its limits. Trump will want more commitment from Germany on its financial obligations to NATO, and if he gets that, perhaps he’ll give a little on other issues. But don’t expect Merkel to turn Trump into Gore on global warming. His energy policies are key to producing an economic boom, and any attempt to turn him on that issue will likely get nothing but polite lip service in return.